As communication technology has developed, mobile phones have become an essential part of human lives. Now the technology of mobile phones is developing faster and faster, various applications emerge continuously and the mobile phone has more complete functions. Like a computer, it usually needs two or more keys pressed at the same time to complete a function during use of a mobile phone. For instance, a function is set by pressing down two keys at the same time to lock the keypad or unlock the keypad. The existing baseband chip of a mobile phone, however, does not support the detection when two or more keys are pressed down simultaneously and is unable to implement the application which can only be started by pressing down two or more keys simultaneously.